1. Field of the Invention
The present invention relates to a method and apparatus for reading multiple bar codes arranged in a fixed order on various components of an object, such as a circuit card. Specifically, the field of view of a bar code scanner is arranged into several fixed areas that enclose bar codes, termed "reading gates". The relationship between each reading gate and a specific component is termed a "configuration". By storing all possible configurations in memory, a processor can then build a pre-defined output data stream for all of the bar codes on a scanned object.
2. Background
It is increasingly commonplace within industry to utilize bar code symbols printed on objects in order to identify the objects and convey information regarding the objects. A conventional bar code symbol comprises a pattern of vertical bars of various widths separated by spaces of various widths. The modulated widths of the bar and space elements can be interpreted by an electro-optical imaging system that converts the symbols into an electrical signal, which is then decoded to provide an alphanumeric representation of the bar code symbol. Bar code symbology of this nature are commonly used in various applications, such as inventory control, point of sale identification, or logistical tracking systems.
The electro-optical imaging system typically uses light from a light source that is scanned across the bar code field. Since the bar code symbology is often disposed on the object to be identified, it is desirable for the reader to be included in a hand-held or portable device so that the reader can be brought to the object. The operator can physically move the light source across the bar code field, such as by use of a light pen. Alternatively, a bar code reader may include movable mirrors that automatically articulate light from a laser back and forth at a high rate to scan across the bar code field. The operator would normally be provided with a feedback signal, such as an audible tone, that alerts the operator as to the successful completion of a bar code reading operation.
Alternatively, electro-optical imaging systems can convert the entire bar code symbol into pixel information that is deciphered into the alphanumeric information represented by the symbol. Such imaging systems typically utilize charge-coupled device ("CCD") technology to convert the optical information from the bar code symbol into an electrical signal representation of the symbol. CCD-based electro-optical imaging systems are preferable over laser-based imaging systems since the CCD does not require any moving elements, and is further adaptable to image advanced types of symbologies, such as two-dimensional codes, that could not be easily collected by an articulated laser. An image of the bar code symbol is optically transferred to a linear or two-dimensional array of multiple adjacent photodiodes that comprise the CCD device, with each one of the photodiodes defining a distinct picture element (or "pixel") of the array. The CCD array is scanned electrically by activating the individual photodiodes in a sequential manner.
In certain scanning applications, a single bar code symbol alone does not convey enough information to the user. For instance, a printed circuit card may contain numerous bar code symbols affixed to specific components of the card. Each bar code symbol may include serial number information for the corresponding component. If the user needs to determine the serial number for a specific component on the card, however, the scanning process does not produce a sufficient output stream of data. Instead, the data output stream includes a set of serial numbers arranged in an order unknown to the user.
One method for solving this problem is to determine the arrangement of components (the "configuration") on the circuit card prior to scanning the card and modify the hardware of the scanner accordingly. Unfortunately, each circuit card may have a different configuration. Usually, the configuration varies according to the manufacturer of the card. Among manufacturers, the configuration may be further varied according to a model number. Thus, for each possible configuration, a different scanner must be used to obtain information about specific components. This method of scanning is extremely expensive and inefficient.
Accordingly, a need exists for a method and apparatus for scanning multiple bar code symbols arranged in a fixed order on an object.
Further, a need exists for a method and apparatus for ascertaining specific bar code information from an object without requiring the use of multiple scanners.